Process Control

What is Process Control ?

- Process control is the use of computers or

microprocessors to control a process.

Process control is used in oil refining, chemical processing, car manufacturing, and temperature control, as well as the food and beverage industries.

There are three types of process control :-

1) Batch process control. This is used in processes where specific amounts of raw materials are combined together and mixed for a certain length of time. An example is the manufacturing of food products such as pre-packaged meals. The ingredients are measured into a large vessel and mixed together for a certain amount of time. They are then heated to cook them. The amount of each ingredient that is added is controlled by computer, as is the length of time for each stage and the temperature. Batch processes are generally used to produce relatively small amount of product per year.

Example of Batch Control System

Manufacturing of food products

2) Continuous process control. Often, a physical system is represented through variables that are smooth and uninterrupted in time. The control of the water temperature in a heating jacket, for example, is an example of continuous process control. Some important continuous processes are the production of fuels, chemicals and plastics. Continuous processes in manufacturing are used to produce very large quantities of product per year (millions to billions of pounds).

Example of control system of a continuous stirred-tank reactor.

3) Discrete process control. This is when specific items are produced. Found in many manufacturing, motion and packaging applications. Robotic assembly, such as that found in automotive production, can be characterized as discrete process control. Most discrete manufacturing involves the production of discrete pieces of product, such as metal stamping.

Discrete process control such as the wheel fitter